1. Field of the Invention
The present invention relates to disk brakes and more particularly to improvements in large area contact disk brakes for vehicles.
2. Description of the Prior Art
The disk brake of the present invention is a disk brake of the type described in U.S. Pat. No. 5,330,034 issued Jul. 19, 1994 and U.S. Pat. No. Re. 35055 issued Oct. 10, 1995 referring to full annular disk brakes for larger vehicles such as trucks. The concept of the full annular disk brake is now proposed for automobiles and light trucks and the present invention relates to a structure of a full annular disk brake for such vehicles.
There are obvious advantages in having a complete annular array of friction pads contacting an annular disk on both sides of the disk. The braking or thermal energy distribution is related directly to the thermal resistance associated with both sides of the interface where the heat is generated. In a full annular brake there is a large area to distribute the braking energy more efficiently.
It has also been found that vibrations between the inner and outer pads are the major causes for brake squeal.
The analysis of vibration response is of considerable importance in the design of brakes that may be subjected to dynamic disturbances. Under certain situations, vibrations may cause large displacements and severe stresses in the brake. The velocity of a vibrating system is in general, proportional to its frequency and hence a viscous damping force increases with the frequency of vibration. Forces resisting a motion also arise from dry friction along a non-lubricated surface. It is usually assumed to be a force of constant magnitude but opposed to the direction of motion. In addition to the forces of air resistance and external friction, damping forces also arise because of imperfect elasticity or internal friction, called hysteric damping, within the body. The magnitude of such a force is independent of the frequency but is proportional to the amplitude of vibration or to the displacement.
In a brake system, dynamic loading produces stresses and strains, the magnitude and distribution of which will depend not only on the usual parameters encountered previously but also on the velocity of propagation of the strain waves through the material of which the system is composed. This latter consideration, although very important when loads are applied with high velocities, may often be neglected when the velocity of application of the load is low. Since dynamic loading is conveniently considered to be the transfer of energy from one system to another, the concept of configuration (strain energy) as an index of resistance to failure is important. One of the important concepts is that the energy-absorbing capacity of a member, that is, the resistance to failure is a function of the volume of material available, in contrast to the resistance to failure under static loading, which is a function of cross-sectional area or section modulus.
One of the main problems in adapting the technology of a full annular brake system of the type described in the above mentioned patents is the consideration of weight and cost. It would be unrealistic, no matter what the advantages, to assume that the a new full annular brake system would be accepted on the market at a price substantially higher than present day disk brakes. Furthermore any increase of weight compromises the fuel consumption.